1. Field of the Invention
The present invention relates to an injector to be used in a fuel injection system for an internal combustion engine, and more particularly to such an injector to which highly pressurized fuel is supplied.
2. Description of the Prior Art
A conventional injector most similar to the present invention has a construction as shown in FIG. 2.
In FIG. 2, the injector includes a casing 2 having a through-hole 2c extending along the axis thereof from a front end surface 2a to a rear end surface 2b. A valve housing 5 is fixedly inserted in the through-hole 2c through the front end surface 2a. A valve 7 is slidably received within the valve housing 5. A fuel pipe 9 is fixedly inserted in the through-hole 2c through the rear end surface 2b. A solenoid coil 10 is disposed in a space defined between an outer peripheral surface of the fuel pipe 9 and an inner peripheral surface of the casing 2. An armature 8 is fixedly mounted to a rear end of the valve 7. A pipe member 14 is fixedly disposed in the fuel pipe 9. A spring 15 is interposed between the pipe member 14 and the armature 8 in a compressed manner so as to forwardly bias the valve 7. While the valve 7 is at its advanced position, the valve 7 closes an injection hole 5a formed at a front end of the valve housing 5. When the solenoid coil 10 is energized, the valve 7 is reawardly attracted through the armature 8 to open the injection hole 5a. The solenoid coil 10 is wound around a bobbin 11.
The injector constructed as described above is supplied with pressurized fuel through a hose 3. In order to prevent leakage of the pressurized fuel to the solenoid coil 10, a first O-ring 12 is provided between a front end of the bobbin 11 and the casing 2 and a second O-ring 13 is provided between a rear end of the bobbin 11 and the fuel pipe 9.
In such a structure, however, pressure of the pressurized fuel acts on the bobbin 11. So long as the pressure of the pressurized fuel is in the order of 2 to 5 kgf/cm2 used in most of the recent fuel injection systems, such a structure will cause no problem. However, when the fuel pressure rises to the order of, for example, 100 kgf/cm2, the bobbin 11 of the structure cannot bear the pressure. More specifically, there is a possibility of deformation or breakage of the bobbin 11.